1. Field of Invention
This invention relates to testable potable water backflow prevention assemblies and the risk of contamination to a potable water supply they pose by virtue of the differential pressure gradient inherent to these devices and the ease with which one may access the water along the differential pressure gradient. This invention prevents unauthorized access to the potable water supply along the differential pressure gradient of testable backflow prevention assemblies.
2. Description of the Prior Art
Testable backflow prevention devices are installed on potable water lines to prevent contamination of the drinking water supply. They are commonly installed after the water meter serving facilities such as high-rise buildings, shopping malls, hospitals, schools, airports, dairies, bottling plants, farms, laboratories, pharmaceutical plants, nursing homes, military bases and commercial and industrial complexes.
Testable backflow prevention devices work by means of multiple check valves and, often, additional devices. There is a differential pressure across any properly operating check valve assembly. Test cocks are located before and after each check valve in testable devices; so as to make sure they are operating properly and will prevent backflow of potentially contaminated water. Although test cocks are intended only for testing the device, and then only by authorized technicians, their significance and function is not generally understood. It is common to see hose bibs and other connections made directly to the test cocks; although such connections are strictly prohibited by water purveyors. These devices are sometimes by-passed, either intentionally or inadvertantly, by connecting two or more test cocks by a common hose or pipe. The hazard of such connections is generally not perceived but is usually substantial. This "Tamper-Proof Backflow Prevention Assembly" is specifically designed to mitigate this hazard as well as provide a suitable level of backflow prevention.
U.S. Pat. No. 3,173,439 to D. G. Griswold et al, shows the operation of a reduced pressure principle backflow preventer; generally considered a very protective type of testable backflow prevention device. There is a differential pressure gradient along this type of backflow prevention assembly and three of the four test cocks along this device will show a different level of pressure. U.S. Pat. No. 3,724,487, to Hunter, and U.S. Pat. No. 3,918,477, to Grams, are examples of some other backflow prevention assemblies.
The concept of safety sealing is not new. U.S. Pat. No. 2,069,849 to P. Rich, illustrates a protector cap for a spigot. With respect to security, locking devices of all sorts have been made; including the mortise and tenon types used to lock such things as automobile wheel rims to fire hydrant caps. More applicable to this patent application is U.S. Pat. No. 3,090,218 to H. A. Birkness. However the application and type of "Locked Safe Valve" of H. A. Birkness is substantially different in several respects. Most notably, it is not specific to or made a part of a backflow prevention assembly. Furthermore, it covers only a specific type of valve and locking mechanism, not found in backflow prevention assembly test cocks or this application.
My previous U.S. patent application titled "Water Access Preventer", Ser. No. 254,574, Filed Oct. 7, 1988, now U.S. Pat. No. 4,878,515, is the first to address the subject of mitigating the risk of contamination of potable water within testable backflow prevention assemblies. The "Water Access Preventer" is a retrofit device for existing testable backflow prevention assemblies. Unlike my previous "Water Access Preventer", this new patent application is for a totally new, and complete, tamper-proof, backflow prevention assembly. Disclosure document No. 211783 of September 1988 discloses essential elements of the "Water Access Preventer" mentioned above as well as this new "Tamper-Proof Backflow Prevention Assembly."